In the mid-1960s, a social scientist noted something ominous that came to be called "Moynihan's Scissors": Two lines on a graph crossed, replicating the blades of a scissors. The descending line charted the decline in the minority male unemployment rate. The ascending line charted the simultaneous rise of new welfare cases.

The broken correlation of improvements in unemployment and decreased welfare dependency shattered confidence in social salvation through economic growth and reduced barriers to individual striving. Perhaps the decisive factors in combating poverty and enabling upward mobility were not economic but cultural  the habits, mores and dispositions that equip individuals to take advantage of opportunities.

This was dismaying because governments know how to alter incentives and remove barriers but not how to manipulate culture. The assumption that the condition of the poor must improve as macroeconomic conditions improve was to be refuted by a deepened understanding of the crucial role of the family as the primary transmitter of the social capital essential for self-reliance and betterment. Family structure is the primary predictor of social outcomes, as Daniel Patrick Moynihan knew in 1965.

Fifty years ago this month, Moynihan, then a 37-year-old social scientist working in the Labor Department, wrote a report, "The Negro Family: The Case for National Action," that was leaked in July. The crisis he discerned was that 23.6 percent of African American births were to unmarried women. Among the "tangle" of pathologies he associated with the absence of fathers was a continually renewed cohort of inadequately socialized adolescent males. This meant dangerous neighborhoods and schools where disciplining displaced teaching. He would later write: "A community that allows a large number of young men to grow up in broken families, dominated by women, never acquiring any stable relationship to male authority . . . that community asks for and gets chaos."

Academic sensitivity enforcers and race-mongers denounced him as a racist who was "blaming the victim." Today, 72 percent of African American children are born to single women, 48 percent of first births of all races and ethnicities are to unmarried women, and more than 3 million mothers under 30 are not living with the fathers of their children.

In 1966, Sargent Shriver, head of President Lyndon B. Johnson's "War on Poverty," was asked how long it would take to win the war. He replied, "About 10 years." The conventional wisdom was John F. Kennedy's cheerful expectation that a rising economic tide would lift all boats. America now knows that bad family structure defeats good economic numbers.

Today, a nation dismayed by inequality and the intergenerational transmission of poverty must face the truth that political scientist Lawrence Mead enunciated nearly 25 years ago: "The inequalities that stem from the workplace are now trivial in comparison to those stemming from family structure. What matters for success is less whether your father was rich or poor than whether you knew your father at all."

Moynihan, undaunted by his shrill critics who stifled debate and research, brought his barbed wit to the subject, suggesting that an important determinant of the quality of American schools was their proximity to the Canadian border. That is, high cognitive outputs, measured by standardized tests, correlate less with high per-pupil expenditure than with a high percentage of two-parent families, which are not scattered randomly.

The election of Kennedy was celebrated in academia as the empowerment of the professoriate. Moynihan ruefully remembered the euphoric expectation of "the direct transmission of social science into governmental policy." We still are far from fully fathoming all that has caused the social regression about which Moynihan was prescient. There has been what he called "iatrogenic government," an iatrogenic ailment being one caused by a physician or medicine: Some welfare policies provided perverse incentives for absent fathers. But the longer Moynihan lived, the more he believed that culture controls more than incentives do.

"The role of social science," he would write, "lies not in the formulation of social policy, but in the measurement of its results." Not in postulating what will work but in demonstrating what does work. And, increasingly, what does not work.

Chastened by "the obstinacy of things," Moynihan recalled a Harvard chemist defining the problem that exists, in the physical sciences and perhaps in social science, when, in Moynihan's phrasing, "the number of variables interacting with one another in any given situation makes that situation extraordinarily complicated and difficult to fathom." Moynihan asked the chemist at what number of variables this problem begins. The chemist replied: "Three."